An internal combustion engine typically has a throttle body and a surge tank arranged in sequence from the upstream side of an intake system, or rather an intake manifold. The intake manifold and the surge tank communicate with one another through an intake manifold stiffener.
One such example of a support structure for an 35 intake system is disclosed in published Laid-Open Japanese Patent Application No. 5-65857. In the support structure disclosed therein, a throttle body-mounting flange portion is provided at a collection portion (i.e., a surge tank portion) of an intake manifold. The intake manifold is made of resin or steel pipe, and has a plurality of individual intake passage portions extending toward the collection portion from an engine body in a downwardly curved manner. The intake passage portions are mounted at downstream ends thereof to the engine body, but are connected at upstream ends thereof to the surge tank portion. In addition, a stay member, whose one end is mounted on the engine body, is engaged at the other end thereof with the above-mentioned throttle body-mounting flange portion. As a result, the intake manifold is supported at the surge tank portion by means of the stay member.
Another example of such a support structure is disclosed in published Japanese Utility Model Registration No. 2518964. The support structure for the intake manifold as disclosed therein includes a surge tank and a branch pipe arrangement. The branch pipe arrangement is integrally connected at the top thereof to the surge tank, while being joined at the bottom thereof to one sidewall of a cylinder head. A reinforcement portion is provided on an outer surface of the outermost branch pipe of the branch pipe arrangement. The reinforcement portion has a greater thickness at a location approximately midway from a proximal end of the branch pipe positioned toward the engine body. Further, an upper support stay extends between a proximal end of the reinforcement portion and an outer end portion of the surge tank. In addition, a lower support stay extends between a distal end of the reinforcement portion and a cylinder block skirt portion or mission case.
In conventional support structures for the intake system of the internal combustion engine and, particularly, in intake manifold stiffeners for supporting the surge tank on the upper sides of branch pipes of the intake manifold, the surge tank being attached on the upstream side of the intake manifold, a great number of intake manifold stiffeners are available that are made of either simply structured metal plates or steel pipes. However, the above-mentioned intake manifold stiffeners are typically unable to control vibrations of the surge tank or throttle body. The surge tank and the throttle body each have respective sensors fitted thereto, and such vibrations are an inconvenience since they can adversely affect the sensors, which is disadvantageous in practical use.
In addition, a large number of the above stiffeners are designed for mounting at two locations in total. More specifically, such an intake manifold stiffener is mounted both on the surge tank at one location and on an engine-mounting flange portion of the intake manifold at another location. The intake manifold is mounted on the engine through the engine-mounting flange portion. Such a mounting method is typically unable to control deformation; therefore there has been a continuous demand for an improved mounting method.
A further inconvenience is that the stiffener cannot be provided at a location which effectively increases the rigidly of the stiffener due to the positioning of an injector, a fuel delivery pipe, a harness, a throttle body, and accelerator cable, etc., on the upper side of the intake manifold. This is disadvantageous in practical use.